1. Field of Invention
This invention relates to a communication system that includes fiber optic and wired mediums.
2. Description of Related Art
Cable communication systems use optical fibers to transmit information between a head-end and a fiber node and use coaxial cable to transmit information between the fiber node and end-users. With increasing need for greater capacity, current systems are stressed to their limits. Thus, there is need for new technology to increase capabilities of communication between head-ends and end-users.
This invention provides a new architecture for a communication system between head-ends and end-users which expands capacity, simplifies transmission and operation, increases reliability and reduces cost of the communication system. A concentrator receives communication signals from a head-end and forwards the received communication signals to either one or more fiber nodes and one or more mini-fiber nodes. End-users communicate with the fiber nodes and mini-fiber nodes via wired connections such as coaxial lines. The connection to the head-end is via a small number of optical fibers (preferably one or two) while a much larger number of mini-fiber nodes may be serviced where a connection to each of the mini-fiber nodes is via one or more optical fibers that provide full duplex communication.
The communication between the head-end and the concentrator may be via digital signals or analog signals. Analog signals are split from the digital signals and sent to the end-users via the fiber node and digital signals are demultiplexed into signals to be transmitted to the end-users via the mini-fiber nodes and the fiber nodes. The fiber node digital signals are modulated onto RF carriers and forwarded to the fiber nodes. Mini-fiber node digital signals are further demultiplexed into signals corresponding to each of the mini-fiber nodes and transmitted to the mini-fiber nodes via respective optical fibers. The mini-fiber nodes may combine the signals received from the head-end with loop-back signals used for local medium access control (MAC) and forward the combined signals to the end-users by inserting those signals into the transmissions from the fiber node.
Upstream digital signals are received by the mini-fiber nodes, demodulated and transmitted to the concentrator. The concentrator multiplexes the upstream mini-fiber node signals using multiplexing techniques such as time domain multiplexing (TDM) or wavelength division multiplexing (WDM) and forwards the multiplexed signals to the head-end. Upstream digital signals may be received by the fiber node and demodulated and multiplexed together with mini-fiber node signals and forwarded to the head-end.
If the head-end communicates with the fiber node via analog communication signals, the concentrator splits the analog signals destined for the fiber nodes from digital signals that are destined for mini-fiber nodes. The analog signals may be frequency converted by shifting the received signals to the proper RF bands and transmitted to the fiber nodes while the digital signals are demultiplexed and sent to respective mini-fiber nodes. Upstream analog signals may be received from the fiber nodes and frequency shifted and multiplexed with upstream mini-fiber node digital signals and sent to the head-end.
The concentrator also receives communication signals from end-users through the mini-fiber nodes that may be destined to other end-users also connected to the mini-fiber nodes. In this situation, the concentrator may include a router that routes the communication signals among mini-fiber nodes without forwarding the information to the head-end. In this way, communication traffic between the concentrator and the head-end is reduced with corresponding increase in efficiency.
Reliability is increased because the concentrator reduces the number of optical fibers required to be connected to the head-end. This shortens the mean-time-to-repair (MTTR) and also reduces cost of the communication system.